function s1_generate_a_series_of_files(){
  for index in {1..100}; do 
  echo "${index}" > "/tmp/new_file${index}"
done
}
function s2_list_4_files_in_long_format_about_account_and_group(){
 ls -l /etc/{passwd,shadow,group,gshadow} |sort
}
function s3_find_items_related_to_given_username(){
if [ -n "$1" ]; then
 grep -E "^$1:" /etc/passwd /etc/shadow | sort
 fi
}
function s4_find_items_related_to_given_group_name(){
if [ -n "$1" ]; then
 grep -e "^$1:" /etc/passwd /etc/shadow | sort
fi
}
function s5_create_groups_for_given_group_names(){
groupadd rnd
groupadd itoperation
}
function s6_create_users_and_set_their_group_as_required(){
users=("adam" "bob" "calvin" "david" "edward")
for user in "${users[@]}"; do
  useradd -m $user
   if [[ "$user" == "adam" || "$user" == "bob" || "$user" == "edward" ]]; then
  usermod -aG rnd $user
   elif [[ "$user" == "calvin" || "$user" == "david" ]]; then
   usermod -aG itoperation $user
fi
done
}
function s7_change_users_shell(){
 for user in "adam" "edward"; do
 chsh -s /usr/bin/sh $user
 done
}
function s8_set_password_change_policy(){
passwd -n 10 -x 60 -w 10 adam
passwd -n 10 -x 60 -w 10 bob
passwd -n 10 -x 60 -w 10 david
passwd -n 10 -x 60 -w 10 calvin
passwd -n 10 -x 60 -w 10 edward
}
function s9_set_password_for_five_users(){
usernames=(adam bob calvin david edward)
for i in $(seq 1 5);do echo ${!i};echo $(( $i-i ));done
echo "${usernames[0]}:$1" | chpasswd
echo "${usernames[1]}:$2" | chpasswd
echo "${usernames[2]}:$3" | chpasswd
echo "${usernames[3]}:$4" | chpasswd
echo "${usernames[$(( $i-1 ))]}:$5" | chpasswd
}
function s10_lock_bobs_password(){
passwd -l bob
}
function s11_include_adam_into_wheel_group(){
usermod -aG wheel adam
}
function s12_change_filesA_permission(){
for index in {3..99..3}; do
 chmod 640 "/tmp/new_file${index}"
done
}
